This invention relates to the electron gun assembly of a plural beam cathode ray tube and more particularly to ruggedizing improvement in a substantially planar electrode member utilized in a multi-beam cathode ray tube electron gun assembly.
Cathode ray tubes of the type commonly employed in color television applications conventionally utilize electron gun assemblies from which a plurality of electron beams are projected to impinge the cathodoluminescent display screen of the tube. In certain gun assembly constructions, the first and second grid electrode members, such being normally control and screen grid electrodes, are often formed as substantially planar components oriented in substantially parallel planes and spaced apart superposed relationship. These electrode members are conventionally affixed to at least two longitudinal insulative support members of the gun assembly by supporting projections extending from the respective planar elements.
In multi-beam guns these planar electrodes commonly have several spatially related apertures formed therein to accommodate the respective electron beams generated within the structure. It is important that these several apertures be accurately and consistently located relative to the related apertures in adjacent electrode members, and to the respective cathode surfaces from which the specific electron beams eminate. Fabrication of the gun assembly involves embedment of supporting projections from the various electrode components into the temporarily heat-softened longitudinal insulative support members; at which time the support members on opposed sides of the assembly are pressured inward toward the electrode elements to force the supporting projections thereof into the support members. The compressive pressure tends to exert a distorting force upon the several electrode members, this being especially critical to the planar members wherein a bowing or arcuate bending effect sometimes results. Such bowing, however slight, changes the aperture locations relative to those in the adjacent electrode members, thereby producing deleterious inter-electrode spacing relationships within the gun structure. These uncontrollable changes in the related aperture spacings are particularly troublesome in in-line gun constructions wherein the first and the second grid electrode members often have related apertures of small diameters and close spacings. Since it is a common practice to utilize planar electrode elements for both the first and second grid electrodes, bowing conditions in one or both drastically aggravate the critical inter-electrode spacing characteristics resulting in pronounced inferior performance of the respective electron guns. Additionally, it has been found that a certain amount of distortion of a planar type electrode member is often aggravated by tube processing procedures and by welding pressures employed in effecting attachment of the electrode component to the associated connective lead in the gun assembly.